Spitfire - Pipsqueak

[Olmec Head]

Firstly, I apologise to head it Spitfire rather than RAF fighters, but I am trying to understand the installation of the Pipsqueak system and the remote contactor as this worked in Spitfires.

 

So, for the Pipsqueak system, I understand that this was a radio emitter which squawked a timed radio ident picked up by ground based direction finders to locate the aircraft.  My technical knowledge is strained beyond that.

 

The remote contactor was set for each time band for red leader, yellow leader, blue and green leader on the quarter segments.

 

 

Image from the Spitfire Site (sorry its a bit big).

 

The website http://www.duxfordradiosociety.org/equiphist/pip-squeak/pip-squeak.html explains this far better than me!  And you probably know this from early forum posts on this over the years.

 

My questions are:

 

When was this fitted and to what aircraft?  I am guessing that the rollout started from September 1939 onwards and that squadron leaders got first issue followed by section leader aircraft and then all squadron aircraft by the BOB.  That is just surmise, so it would be good to see if anyone has any better ideas and references.  I did find a Google reference to  Pipsqueak for Feb 40:

 

'28/02/40Crashed into North Sea in Spitfire Mk I L1051 went down into the sea, probably between the Outer Dowsing and East Dudgeon lightships, from where the last "pipsqueak" transmission was heard. '

 

The Pipsqueak system worked with the HF TR9D radio, so was it then adapted to work with the later VHF radio systems?  All later Spitfires seem to retain the remote controller box, so I assume it was a still functioning system from later 1940 onwards and presumably fitted to all Spitfires as a standard item.  I think I remember a post by Edgar that the Remote Contactor was not removed as a modification until late 1944 and then only for XVI, but I may well be misquoting him.

 

I won't even start to ask about the fitment to Spitfires outside of Fighter Command and the ADGB area and to USAAF Spitfires that is too far! 

 

Now to watch the BBC programme on Hornby and Airfix, sadly much of it is about trains, I understand that there is a fight over trains this episode, which may make trains more exciting.

Edited March 13, 2019 by Olmec Head

[Smithy]

I can't answer all your questions right this minute without going and digging out books but hopefully this helps a bit. Pipsqueak was installed with both the TR.9D HF and TR.1133 VHF sets. The disadvantage with earlier HF set (apart from only having a range of around 35 to 40 miles and poor reception) was that it only had 2 channels of which only one was voice, the other having to be for Pipsqueak. For ease of control each squadron was operating a separate frequency so the lack of channels meant that HF equipped squadrons couldn't talk to each other in the air. Obviously in this situation wing coordination was difficult to say the least. The VHF set had four channels.

 

With Pipsqueak the clockwork timing device attached to the radio would broadcast a constant tone for 14 seconds in every minute. There were special receiving stations in each sector which would pick up these signals and give bearings for the sector to triangulate on. Each squadron in a sector would have its Pipsqueak broadcasts synchronised so they didn't overlap. This obviously meant that effective control in a sector was limited to no more than four squadrons at a time.

 

If you want dates I'll have to burrow around in my things.

Edited March 13, 2019 by Smithy
Spelling

[Dave Swindell]

15 minutes ago, Smithy said:

This obviously meant that effective control in a sector was limited to no more than four squadrons at a time.

My understanding is that one radio channel in the aircraft was dedicated to Pipsqueek.

Each squadron in a sector would have their aircraft channel tuned to the same frequency, and could designate one of 4 sectors to each squadron section (flight).

The number of squadrons which could operate the system in a particular sector would therefore be governed by the number of frequencies available to tune the radios to, not the 4 sectors within each frequency.

The frequencies could be re-used in other sectors out of effective range of the ground receiving stations.

VHF is typically shorter range than HF, but gives better reception when iin line of sight.

[Smithy]

1 minute ago, Dave Swindell said:

My understanding is that one radio channel in the aircraft was dedicated to Pipsqueek.

Each squadron in a sector would have their aircraft channel tuned to the same frequency, and could designate one of 4 sectors to each squadron section (flight).

The number of squadrons which could operate the system in a particular sector would therefore be governed by the number of frequencies available to tune the radios to, not the 4 sectors within each frequency.

 

I mentioned how one channel was reserved for Pipsqueak which was a problem for HF set equipped units as they couldn't communicate with other squadrons in the air. When the TR.1133 VHF set arrived it had four channels (although two were reserved for "Guard" emergency broadcasts).

 

As I also said, each squadron in a sector would have its Pipsqueak broadcasts synchronised so they didn't overlap. This meant that 4 squadrons could broadcast Pipsqueak for a separate 14 second period in every minute. As I also mentioned each sector had its own dedicated receiving stations for Pipsqueak which meant that sector controllers could only effectively control and marshal 4 squadrons within a sector effectively without signal confusion.

 

Two of the better sources for information concerning sector control including radio command and control are, AIR 16/186 and AIR 20/222

[Dave Swindell]

Hi Smithy

I was repeating your points where I was in agreement with you so you could see where my thoughts differed.

 

I still don't see why you're limiting control to only 4 squadrons.

11 hours ago, Smithy said:

As I also said, each squadron in a sector would have its Pipsqueak broadcasts synchronised so they didn't overlap.

That's not correct, the synchronised timing of the signal was for each section of the same squadron operating on the same frequency.

 

With the HF setup the radios had only two channels, and one was dediated to pipsqueak.

However, these channels could be tuned on the ground to set frequencies over the full frequency range.

Each squadron would operate pipsqueak on a different frequency, and the timing of the signal would indicate which section (red, blue, yellow, green) was being tracked - ie 4 sections could be tracked on the same frequency.

Ground control would need 3 sets in the 3 monitoring stations tuned to the same squadron frequency to track all 4 squadron sections.

To track another squadron they would need another 3 sets in the same monitoring stations tuned to the other squadron's frequency.

The limitation is the number of receiving sets available at each monitoring station (and the trained staff to operate them).

If 4 sets available then yes, you're limited to 4 squadrons, but if you have 6 sets you could monitor 6 squadrons.

 

[Smithy]

I think you misunderstand the RAF sector command and control system. The limitation is not on the range of frequencies but rather on the fact that each squadron broadcast Pipsqueak so that their broadcasts did not overlap with another in the same sector that they were controlled by. Because Pipsqueak signals were broadcast over a 14 second interval this limited effective sector control without signal confusion to 4 squadrons. All of this information can be found in the two actual AM documents I listed above.

[Dave Swindell]

Hi Smithy

I've been doing a bit more reading into this and it does appear I've misunderstood some of the operational aspects of Pipsqueak, in particular the Red, Yellow, Blue and Green being applicable generally to Squadrons, and not Flights (above post edited).

The technical aspect I understand, it's basic radio direction finding, tracking 4 units based on their different transmitting periods.

 

All that I've read so far (and like most, I don't have access to the AM's you quote) would seem to indicate that pipsqueak was limited to one frequency per sector due to there only being 3 receivers per sector, this largely being due to the lack of supply of CRT's for display indication. It's easy with hindsight to say just use more frequencies to give control of more units, and forget that certain parts of the hardware were cutting edge technology at the time and in very short supply.

 

To answer some of the OP's questions @Olmec Head, the first 5 sector ground stations were operational by the end of 1937, and after proof of its effectiveness the Air Ministry gave the go ahead for equiping the rest of the sectors in March 1938.

Effective IFF generally superceded Pipsqueak, being available at the beginning of the Battle of Britain and rapidly installed over much of the RAF fleet at the end of the Battle.

Pipsqueak was retained after IFF was installed for tracking in areas where there wasn't radar coverage and locating and directing lost airmen.

With the fixed ground infrastructure required for it's use for command and control I'd think that it was only ever used in this capacity in the UK and by Fighter Command.

From a production point of view it would be installed in all Spitfires being manufactured up until the point it was discontinued, if Edgar quoted late 1944 that is most likely correct.

[Olmec Head]

Thanks to Smithy and Dave for providing some further use information on Pipsqueak.

I have had a bit of a Google trawl on pilot notes air pubs for the various Spitfire marks and here are some of my tentative ideas and further questions:

Early Spitfire Mark One: No Pipsqueak fitted pre-war and hence no remote contactor in cockpit.

Spitfire Mark One:  Gradual fitting of Pipsqueak over later 1939 and early 1940 with full equipment of airframes by late 1940.  (bit of a guess on that timescale.)

Spitfire II.  All airframes fitted with remote contactor in cockpit during frontline Fighter Command Service.  (It would be interesting if OTUs and other second line units operated Pipsqueak and if not would they remove the equipment and remote contactor).  The PS and remote contactor seems to have continued alongside the new IFF systems.

Spitfire V.  Again, I would presume that all UK based Vs would have the PS system in place alongside the IFF systems. 

But Would non UK based RAF Spitfires been equipped with PS and the RC, i.e in the Western Desert , Med Malta and the Far East?

And what about USAAF Spitfires in the MTO?

Spitfire VI.  PS and RC in place?

Spitfire VII.  In place over type’s operation service.

Spitfire VIII.  The pilot notes show the remote contactor in place.  But:

Would the system have been used in the Desert Air Force and Med? 

Would USAF Spitfire VIIIIs been equipped Would it have been used in the Far East and Burma? 

Would the RAAF Spitfire VIIIs been equipped with Pipsqueak? 

Spitfire IX.  Pilot notes show the system in place.

Spitfire XII:  Pilot notes show system in place.

Spitfire XIV:  I could not find access to the XIV pilot notes, but I would guess the 1944 UK ADGB based aircraft were fitted - but with the system not continuing after late 44 with ops moving to Europe.

Spitfire XVI and 16.

The pilot notes for the XVI are combined with the IX, so it's hard to know if it is a XVI cockpit.  From an early Britmodeller post by Edgar he stays that the XVI was not equipped from later Dec 44 which makes sense that the system would not be used when based in liberated Europe

A Google search found me a Spitfire 16 (presumably Low back) manual from 1949 with no RC fitted in the cockpit.  This would suggest that the system was not fitted in the post-war period.

Spitfire 18:  The SAM Modellers datafile book on Griffon Spitfires shows no remote contactor in the cockpit photos or diagrams,

Spitfire 21:  More difficult as the only image I could find was again the SAM book and the pilot notes reproduction did not show the full starboard cockpit side, but there could be a remote contactor box bottom edge.  You pay your money and you take your choice!  Possibly UK based late war Spitfire 21s had the system but not postwar.  Again I think Edgar reckoned that the XIV and 21 stopped being fitted.

Spitfire 22/24:  Again the SAM book images show no remote contactor.

Sorry but I did not look at any PR variants.

All that for: do I put a little black box with a white and red circle on my 1/48 Spitfires!

Edited March 15, 2019 by Olmec Head